Coated copper article and method of making the same



Patented May 21 1935 COATED COPPER ARTICLE AND METHOD OF MAKING THE SAME Robert B. Tanner, Highland Park, and John S. Thompson, Detroit, Mich assignors to Metal Flnlshingncsearch Corporation, Detroit, Mich, a corporation of Michigan Application June 4, 1934,

Serial No. $8,978

Claims. (c1. 148-6) This invention has for its object-an article having a surface of copper or copper alloy with a paint-holding coating chemically formed thereon, and a method of forming such coating. The ob-. ject of the invention is to provide articles with surfaces of the kind described which canbe finished or decorated with any desired siccative coatenable to employ a soluble compound of copper toaccelerale the action of the solution and the coating is further improved by an oxidizing agent which is compatible with the solution. Any oxidizing agent which does not introduce an-objectionable metal or other compound and which does not oxidize the acidused can be employed in suitable proportions. Sodium'sulphite, sodium nitrite and sodium nitrate are readily available compounds of this character although, if the nitrate is employed with oxalic. acid, the solution should not be heated above the temperature at which the oxalic acid is oxidized. ,Of course. similar observations apply with other oxidizing agen and other acids of the group described.

There may be considerable variations in the proportions of the acid and other ingredients'in the solution, but a proportion which is satisfactory with the group of acids in general is about a:

15% solution of the acid with 1% of sodium nitrite and about 1/2 of 1% ofcopper sulphate. The solutions coat best when hot, but, as observed abov the nature of the oxidizing agent and of the. acid being used must be considered in deciding upon the temperature to employ, in order to avoid exhausting the strength of the oxidizing agent and the acid upon each other instead of on the coating operation.

The surface of a copper or copper alloy article dipped in a hot solution of the kind described for ten minutes has formed thereon a substantially integral coating to which paint, varnish or similar siccative coats adhere with great tenacity. 5 The time necessary for. the coating will, of course, vary with the, strength of the solution, the proportions and nature of the materials used, etc., but the ten minutes mentioned is a fair working time with many typical solutions of this kind. v

Apparently the coating formed in the 'manner' described above is essentially a copper salt-of the acid employedfor the coating operation.

What we claim is:-

'1. An article having asurface of copper or 15 copper alloy coated with a substantially integral coating of a salt of copper and acid of the group consisting of dicarboxylic and hydroxydicar boxylic acids of the aliphatic series and carboxylic acids, having one carboxyl group,.and-sulphonic 20 acids of the aromatic series, and benzene-'phosphonic acid.

2. The method of coating surfaces of copper or copper alloy, which consists in subjecting the sur-.' face to a solution of an acid of the group consistg5 ing of dicarboxylic and hydroxydicarboxylic acids of the aliphatic series and carboxylic acids, having one carboxyl group, and sulphonic acids of the aromatic series, and benzene phosphonic acid,

said solution containing a soluble compound of 30 copper.

3. The method in accordance with claim 2, and

in which the solution contains a compatible oxidizm t.

or copper alloy, which consists in subjecting the surface to a solution of oxalic acid, containing a soluble compound of copper and a compatible oxidizing agent.

5. The method of coating a surface of copper 88 4. The method of coating a surface of copper 

